1. Field of the Invention
The present invention relates to an electrostatic recording apparatus for forming a recording image by transferring a developing agent conveyed along a predetermined path to a recording medium in accordance with recording data.
2. Description of the Related Art
A multi-stylus printer is conventionally known well as one of electrostatic recording apparatuses. In the multi-stylus printer, a multiple of styluses are aligned at a small pitch in the main scanning direction to constitute a recording head, voltages are selectively applied to the styluses in accordance with recording signals, and discharge is directly performed to a copy sheet to form an electrostatic latent image. In this case, special paper coated with an agent having a high electric resistance is used to easily and stably hold electrons on the copy sheet. However, letters and figures cannot be written well on such special paper with a pen or pencil. Also, since the special paper is denatured depending on the environmental conditions, e.g., the humidity, it cannot be kept for a long period of time. Hence, the special paper is not preferred for office use.
When a gap between the distal ends of the styluses and the surface of the copy sheet is large, the discharge electric field is spread to increase the size of dots to be formed, making it difficult to obtain a recording image having a high resolution. For this reason, a gap material is provided on the surface of the copy sheet and brought into slidable contact with the distal ends of the styluses, thus ensuring a small gap. In this case, however, the distal ends of the styluses are worn.
Thus, as an electrostatic recording scheme with which plain paper can be used and a small gap can be correctly maintained between the image medium and the distal ends of styluses, a scheme with which a toner image is formed on a drum-shaped intermediate recording medium and the toner image is transferred to the copy sheet is used. When this scheme is employed, the size of the entire apparatus can be increased as it uses the intermediate recording medium. Thus, a process of performing recording and development simultaneously is usually employed to avoid an increase in size of the apparatus. Mostly in this case, recording electrodes are aligned in the widthwise direction (main scanning direction) of the developing agent transfer path and the developing agent is transferred from the recording electrodes to the surface of an opposite electrode serving as the intermediate recording medium, thereby forming a toner image. With this scheme, since the electrode-to-electrode gap between the recording electrodes and the opposite electrode affects the density of the image or background smearing, the gap must have a constant appropriate width throughout the entire portion of the widthwise direction. That is, if the electrode-to-electrode gap is excessively narrow, although a high density can be obtained, background smearing occurs. Inversely, if the electrode-to-electrode gap is excessively wide, although no background smearing occurs, a high density cannot be obtained.
The opposite electrode usually forms a drum so that it can also serve as the recording medium. When the opposite electrode drum is rotated, the circumferential surface of the opposite electrode swings in the axial or circumferential direction to change the electrode-to-electrode gap. Also, a small projection can be undesirably formed during the manufacture on the developing agent convey path along which the recording electrodes are located. In this case, the recording electrodes are moved close to the opposite electrode by a distance corresponding to this projection.